Hissing noise from braking system

My Punto has covered 35,000 kms and since the last 1000 kms I have been hearing a hissing noise from the right side near the aircon vent, its not exactly thru the vent but in that area This hissing noise begins when the engine is started and the reason I have said it maybe attributed to the braking system is because the noise stops when I touch the brake pedal. Braking otherwise is normal and I don't have any issues. The noise it faint but I know it is a new noise and hence my attention is drawn.
I suspect it could be the brake booster or the vacuum generator. What could it be?
Abdul

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Hey Abdul I am also getting this noise. Could you please post photographs of your brake booster from inside. I mean take the photo of your brake paddle from inner side.

You will see the linkege connected to brake booster. On the linkage you will get small holes with gause.
The holes and its gause should be clean & colour should be white.
If there are oil stains then I fear that there is minor leakage in brake booster from inner side.

So there is hissing noise of vaccum leak & oil stains on the gause of brake booster from inner side.

I am going to visit TATA . I will compare with other cars then update it.